Regulation of complex host dynamics by a macroparasite

The impact of a macroparasite on a host population which can exhibit highly complex dynamics is considered. We focus on the case where the host reproduces annually, in which case we couple within-season density dependent interactions with a discrete-time pulse to reflect seasonal reproduction. Results from analytic arguments, supported by extensive numerical simulations, indicate that within season parasite-induced host mortality is potentially capable of stabilising and simplifying host dynamics. Moreover, the interaction of demographic processes occurring on different time-scales is, in some cases, stabilising. In particular, parasite reduction in host frequency, which is a destabilising process in the May & Anderson continuous time model, is found to stabilise host macroparasite interactions under certain conditions. These results are discussed in an ecological context.